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How to: Convert Intank Fuel Filter (05+ LGT/OBX 08+ WRX/STI) to Engine Bay Filter


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Subaru moved the fuel filter to the fuel tank for in 2005 for Legacy's, Outbacks and STI's. STI's got it easy though, it's very simple to remove the fuel filter and replace it with a piece of submersible hose. Legacy's on the other hand received a whole new bucket assembly that requires a lot of work to bypass. In 2008 Subaru moved WRX's and STI's to this same bucket setup.

 

Subaru claims that the fuel filter never has to be replaced, but anyone who has worked with cars knows that they should be replaced occasionally, especially outside of the US. Replacement fuel filters cost $75+ and take a lot of work to remove and replace. For this reason I stared looking to convert back to the engine bay fuel filter found in older Subaru's.

 

Item list:

1 x $12 - 10" to 14" Plastic Corrugated Fuel Flex Hose, can get them at Auto Performance Engineering.

1 x $1 - 11.3mm Oetiker Clamp (Clamping range 9.6mm-11.3mm)

1 x $1 - 14mm Oetiker clamp (Clamping range 11.5-14.0mm)

1 x $10 - Engine bay fuel filter from WRX/FXT

1 x $8 - 5/16" Fuel injection hose

1 x $6-$20 - Pliers for Oetiker clamp (I used Click-R Type Pliers)

Total = $32 without pliers, next years fuel filter replacement $10...

 

It's always a good idea to buy a spare parts (I bought 3 hoses in different sizes and tested fitment with them all).

 

Exploded view of the fuel pump assembly

http://legacygt.com/forums/attachment.php?attachmentid=258360&stc=1&d=1510889111

 

Fuel pump and filter without the tub

http://legacygt.com/forums/attachment.php?attachmentid=258355&stc=1&d=1510889111

 

Fuel filter is inside of this plastic

http://legacygt.com/forums/attachment.php?attachmentid=258356&stc=1&d=1510889111

 

I was trying to gracefully remove the plastic, but it didn't budge and had to be cut off. This fuel filter is from a car with 30k miles, look how dirty it is still.

http://legacygt.com/forums/attachment.php?attachmentid=258357&stc=1&d=1510889111

 

Before I found out about the wonderful corrugated plastic hoses, I was gonna use submersible fuel injection hose ($20 a foot!). I drilled out the hole to accommodate for that hose. You will need to drill the hole out a bit to fit the corrugated plastic, but not this much.

http://legacygt.com/forums/attachment.php?attachmentid=258358&stc=1&d=1510889111

 

Original idea was to use the 5/16" submersible fuel hose and attach it to the stock corrugated plastic hose. But I couldn't find a reliable way to clamp it on (no barbs on stock plastic end).

http://legacygt.com/forums/attachment.php?attachmentid=258359&stc=1&d=1510889111

 

When I decided to just remove the stock fuel hose, I found that our fuel pumps are 5/16", but the nipple on top is actually 3/8".

http://legacygt.com/forums/attachment.php?attachmentid=258361&stc=1&d=1510889111

 

I spent weeks looking for something that could work, even bought 3" of the submersible 3/8" hose. In the end, I used the connector from the factory corrugated plastic hose and heat gun to expand the 5/16" hose to be 3/8", Don't heat the flex joints!

http://legacygt.com/forums/attachment.php?attachmentid=258362&stc=1&d=1510889111

 

Fuel pump end is 5/16", I dipped the hose into hot water to soften it enough to be able to slide it onto the pump easier. Once again don't heat the flex joints.

http://legacygt.com/forums/attachment.php?attachmentid=258363&stc=1&d=1510889111

 

Had to cut the filter assembly a little more to clear the Oetiker clamp, after that fit perfectly

http://legacygt.com/forums/attachment.php?attachmentid=258364&stc=1&d=1510889111

 

Update: Heatshrink the hose on this part and use an Oetiker clamp, regular fuel injection clamp didn't hold the fuel pressure.

http://legacygt.com/forums/attachment.php?attachmentid=258371&stc=1&d=1510889111

http://legacygt.com/forums/attachment.php?attachmentid=258372&stc=1&d=1510889111

http://legacygt.com/forums/attachment.php?attachmentid=258373&stc=1&d=1510889111

 

Looks confusing eh?

http://legacygt.com/forums/attachment.php?attachmentid=258365&stc=1&d=1510889111

 

The return drain hooks right back up no problem.

http://legacygt.com/forums/attachment.php?attachmentid=258366&stc=1&d=1510889111

 

The fuel hose needs to fall in between the plastic bends or it wont clear the bucket, this is why a 12"+ hose is needed.

http://legacygt.com/forums/attachment.php?attachmentid=258367&stc=1&d=1510889111

 

 

There needs to be space between the top and the hose, because the assembly compresses when you install it. This is where 15" hose was getting a little long, luckily I found space to move it around and not hit the roof.

http://legacygt.com/forums/attachment.php?attachmentid=258369&stc=1&d=1510889111

 

Update: I switched to use Oetiker clamp, don't use fuel injection clamp it wont hold the fuel pressure.

http://legacygt.com/forums/attachment.php?attachmentid=258370&stc=1&d=1510889111

 

Finally all together and somewhat fitting well

http://legacygt.com/forums/attachment.php?attachmentid=258368&stc=1&d=1510889111

 

Continued in next post, with engine bay fuel filter install.

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05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Fuel Pump Assembly Installation

 

Pulled the rear lower cushion out, it was a mess, took a shop vacuum to it.

http://legacygt.com/forums/attachment.php?attachmentid=258381&stc=1&d=1510889763

 

There are two black doors, fuel pump is on the passenger side.

http://legacygt.com/forums/attachment.php?attachmentid=258388&stc=1&d=1510889828

 

Looks like mice have been busy, used the shop vacuum to clean it out too. This is actually important because all of that crap will fall into your fuel tank!

http://legacygt.com/forums/attachment.php?attachmentid=258382&stc=1&d=1510889828

 

Pull the fuel pump fuse and idle the car till she dies, this should get rid of most of the fuel in the fuel lines. It is not sufficient to just unplug the fuel pump plug! I did that and the car kept on idling still (but struggling), plus threw a CEL.

 

It is much wiser to do this install on 1/2 or less full tank. I just got back from a highway trip and wanted to replace the pump before another road trip. I drove 25 some miles (should have been 1 gallon used) and it still was way too full, lets just say my driveway got a ton of gas on it...

http://legacygt.com/forums/attachment.php?attachmentid=258383&stc=1&d=1510889828

 

Stock fuel pump assembly in it's glory, it looks pretty clean not yellow like a lot of them tend to be. I wonder if it was replaced anytime recently.

http://legacygt.com/forums/attachment.php?attachmentid=258384&stc=1&d=1510889828

 

Modified assembly ready to be installed. The rubber gasket has nipples and the spacing varies, thus it only installs one way to the metal bracket. For this reason it's a good idea to attach the rubber gasket and metal bracket before you try to stick it in the fuel tank.

http://legacygt.com/forums/attachment.php?attachmentid=258385&stc=1&d=1510889828

http://legacygt.com/forums/attachment.php?attachmentid=258386&stc=1&d=1510889828

 

After some fighting finally got her in and tightened and hoses plugged up

http://legacygt.com/forums/attachment.php?attachmentid=258387&stc=1&d=1510889828

 

I started and idled the car for a good 20 minutes to make sure it was happy, fuel pressures seemed in order too. Went for a drive watching the wideband making sure it wasn't leaning out, after that gunned it a ton and took her on a 15mile highway trip, all went flawless. I'm keeping the stock fuel pump assembly in the car just in case still though :lol:.

 

Learning views are still looking the same so far, will drive for a while and will see if they change. AFR's were about the same too, which means the previous filter was not too clogged, which is a good thing. Guess will see if it was clogged enough to hurt my gas mileage though.

 

 

 

 

Engine Bay Filter Installation

Now that the fuel tank filter is bypassed you need to add a filter in the engine bay. Do not run the car without a fuel filter, you can clog up the fuel injectors. Also make sure to read the manual and verify which line is the feed line and which line is the return line.

 

Items needed

~12" of 5/16" Fuel injection hose: $8/foot usually, try to find a similar box as pictured you get 18" for similar price.

Fuel line Clamps: $2

Fuel filter: $12 (store brand)

http://legacygt.com/forums/attachment.php?attachmentid=258377&stc=1&d=1510889828

 

First thing is to drain the fuel out of the fuel lines, the easiest way to do it is to pull the fuel pump fuse (in the engine bay fuse box) while either the car is running, or start the car with the fuse pulled and let it die. This will consume just about all of the fuel in the feed line.

 

Stock fuel lines, top one is the fuel feed line, center one is the EVAP line, and lower line is the fuel return line that goes to the FPR. Connecting the fuel filter to the wrong line will net you without any filtration, which can lead to clogged injectors. The order may be different on your car, verify with your factory service manual. BUT I have found inconsistencies in the manual between which line is which in my 2005 manual (some pages say top hose is feed, some pages say bottom hose is the feed hose).

http://legacygt.com/forums/attachment.php?attachmentid=258374&stc=1&d=1510889828

 

Remove the the fuel injection clamp, you will need a couple more, get them at the dealer on any auto parts stores.

http://legacygt.com/forums/attachment.php?attachmentid=258375&stc=1&d=1510889828

 

If your line is stuck, like mine was, carefully use some pliers to carefully break the line loose by rotating the line.

http://legacygt.com/forums/attachment.php?attachmentid=258376&stc=1&d=1510889828

 

Fuel filter should be properly labeled, if it's not for these filters the center hole is the out to the fuel rail, and the offset one is the feed from the pump.

 

First attempt and at the install, sadly the stock line is not long enough to reach in front of the battery.

http://legacygt.com/forums/attachment.php?attachmentid=258378&stc=1&d=1510889828

 

Decided to put it closer to the FPR, ziptied it to the TMIC holder (will need to figure something better out later).

http://legacygt.com/forums/attachment.php?attachmentid=258380&stc=1&d=1510889828

 

All done with the FP gauge attached to the return line:

http://legacygt.com/forums/attachment.php?attachmentid=258379&stc=1&d=1510889828

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05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Subbed for another great write-up. I just don't know how you have the time!

 

My time is cheaper then paying a shop to do it, plus I'm a tinker by nature so this kind of stuff is actually fun :spin::lol:

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Forgot to mention that, I got the fuel hoses at Auto Performance Engineering.

 

You can find them at this page, labeled as Flex House. I would buy three 10.87" ones, 14.80 is a little too long and 8.78" is a little too short. Three because you can easily mess them up while heating them up :).

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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  • 1 month later...

I'm just about ready to perform this mod, just need to decide where to mount the filter! I purchased the hose, clamps and crimp tool reccomended by Covertrussian. I decided to use a Fuel Lab In-Line filter, because it gives the option to use a 40 micron / stainless steel element, for E85 compatibility.

 

It seems the best place for the filter may be in the trunk. That would minimize the amount of plumbing under the hood, hopefully keeping fuel temps lower.

 

I know you can get adapters for the fittings on the fuel pump to allow the use of AN hose/fittings. Just not sure how to go about getting the lines from the pump ran back to the trunk.

 

Any ideas on how to route those lines? Maybe someone has done it for a surge tank?

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What crimping tool did you get by the way? I need a better one for oetiker clamps.

 

As for mounting in in the trunk, you will have to cut oem plastic lines under the seat. Middle one seen here:

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Fueling/Fuel%20Pump/SAM_7517.jpg~original

 

IMO it's too much work to put it in the trunk. But I agree engine bay doesn't have much room, hence I'm considering on how to redo my filter right now.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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Looks similar to what I got from HF, sadly it didn't do good consistent pinches, always lopsided, and they were too big for the smaller clamps, thus I mainly use them for axle boot clamps now.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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  • 1 month later...

Awesome write up! Was extremely helpful. (This is problem the biggest thing I personally have done to my car myself) I did everything in one afternoon, I picked up a sspare fuel pump assembly to delete the fuel filter and upgrade the pump too. (Defiantly louder then the stock pump when it primes) the only issue I had was the new assembly wouldn't compress as much as the stock one(I got it close) took alittle love to get the tank sealed and everything tight again.

 

Thanks agian for the great write up.

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  • 3 months later...
  • 6 months later...

Hey guys,

 

I've just heated the white plug end of the 3/8" hose on mine, I found that I was successfully able to remove the hose however the hose end is now quite hard.

 

Did you guys find that after heating the flex hose as well ?

 

Not sure if this is going to make a decent enough seal. Anyway, I'm thinking of grabbing a 3/8 - 5/16 reducer and then getting a short length of 5/16 flex hose locally to go to the top of the pump...

 

If that doesn't work then I've got some longer 3/8 and 5/16" lengths coming from APE.....

 

Great idea covertrussian :)

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Let me know what kind of reducer you find. I bought 3/8" submersiable fuel hose just in case, and was thinking about running a 3/8 to 5/16 adapter if the current system didn't work out. It leaks a tiny bit for me right now, but not enough to worry about.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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I did notice that once you heat the flex hose it gets very hard. I was careful to only heat the end of the hose, just enough to stretch it on to the fitting.

 

How would I just if mine is leaking? Is there a test I could do?

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Prime the fuel pump while it's not bolted all the way down into the fuel tank. You will see fuel spraying out or air bubbles.

 

The very first attempt at this fuel was spraying out, that was with a typical fuel hose clamp. After that I reheated it and reshaped it a little and more importantly added oetiker clamps and now it just bubbles a little.

05 LGT 16G 14psi 290whp/30mpg (SOLD)

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

22 Ascent STOCK

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